1. Field of the Invention
The field of the invention is circuit card supports and in particular, a circuit card support for removably holding an auxiliary circuit card parallel to a host circuit card.
2. Background Art
With large or complex electronic circuits it is frequently desirable to divide the circuit into several electrically interconnected subcircuits each contained on a separate circuit card.
The use of multiple, separate circuit cards provides several advantages. Individual cards may be replaced, reducing repair costs or allowing customized or expanded operation through the connection of optional circuit cards. Circuit functions may be separated, permitting ready isolation of faults. And, the use of multiple circuit cards may allow efficient packaging and improved mechanical resilience of the final product.
One method of connecting multiple circuit cards is through the use of a "mother" board having a plurality of "edge card" connectors on it surface. These connectors on the mother board receive mating connectors positioned along one edge of each of a number of "daughter" boards. The daughter boards fit perpendicularly against the mother board and are generally parallel to save space. An individual daughter board may be removed or replaced by sliding it out from between its neighboring daughter boards, away from the mother board.
The mechanical stability of this system may be increased by supporting the edges of the daughter boards in a card cage. The cage may have a plurality of guide rails for receiving the edges of the daughter cards as they are inserted or removed from the mother board and thereby reducing potentially damaging torque on the edge connectors. A card cage design is described in U.S. Pat. No. 4,716,495 entitled "Printed Circuit Board Chassis with Power Interlock", 4,716,495, assigned to the same assignee as the present invention.
The use of a card cage is most practical in situations where there are several daughter boards and the daughter boards have similar length and width. If a single auxiliary circuit card is to be connected to a host circuit card of different dimensions, other methods are usually adopted, such as the use of columnar standoffs attached to receiving holes in each circuit card to hold the cards separated but parallel to each other. Removal of a card attached by means of such standoffs is relatively difficult and usually requires that the auxiliary card be accessible in a direction normal to its surface. Each standoff must be unscrewed or unsnapped from its respective receiving hole. The subcircuits of multiple circuit cards may be electrically interconnected by connectors attached to a flexible cable or harness. The use of a flexible harness is required if the insertion axis of the connector to the auxiliary card is different from the insertion axis of the auxiliary card to the host card.